Wind turbines, like generally any driven system, have bearings between the driven components (motor/gearbox) and the static components (for example housing). Particular requirements are made of the bearings of wind turbines. The bearings must namely to a particular extent withstand high forces acting in different directions. Due to the irregularity of wind with respect to its strength and direction, which can change within a short time, forces of different strength continually occur in the tension, compression and transverse direction, which are greater the stronger the wind force and the larger the wind turbine. During storms or hurricanes, wind turbines must even withstand extreme loads. The components here must survive the loads without damage over a long operating time. In addition, the bearings of wind turbines have the task of reducing the noises due to the forces acting and generated by vibrations of the wind turbine.
The drive shaft of wind turbines is subjected to high forces and torques, which are transmitted to it by the rotor blades. In order that the drive shaft, and the parts connected to it, do not suffer from excessive material fatigue and become destroyed, they must be correspondingly supported on bearings. The bearings here must absorb and, if possible, neutralize or offset the forces and moments. The bearings must transmit forces in the radial z/y direction and be as soft as possible in the axial x direction in order to be able to compensate for the bearing play present in the pedestal bearing without major restoring forces. Three-point bearing systems are frequently used.
In a typical modern three-point bearing system of the prior art, the shaft carrying the rotor runs through a pedestal bearing and enters the gearbox. The gearbox block is connected to the bedplate on both sides of the gearbox block by means of the gearbox torque brackets. In general, a torque bracket is present on each side. The torque brackets have holes at their ends. The actual clamping bushings, through which is passed an axle, which is itself attached to two supports in front of and behind the torque brackets, are located in these holes or eyes. The axle can be screwed directly to the support, for example by means of radial screws.
Whereas the clamping bushing rests in the eye of the gearbox torque bracket, the axle is supported in the cylindrical cavity of the bushing. The bushing itself is made of materials which also have elastic properties and are thus capable of compensating for and cushioning the forces and moments.
The bushings, as undivided solid bushings, are pressed axially into the supports provided with holes or also, in the form of divided bushings, tensioned radially in horizontally divided supports.
However, there are also designs in the prior art in which a bushing bearing system is provided on both sides of the gearbox bracket. The clamping bushings in this variant are introduced into the two supports on both sides of the torque bracket. In accordance with the prior art, these are, as undivided solid bushings, pressed axially into the supports provided with holes (eyes) or, in the form of divided bushings, tensioned radially in horizontally divided supports.
DE OS 1 955 308 discloses bushings which consist of concentric, rubber-coated half shells and can be used for use as spring element or joint bushing having extremely large steering lock angles in relatively light vehicles.
EP 1 046 832 discloses cylindrical clamping bushings capable of being tensioned radially which are rotationally symmetrical in the tensioned state, consisting of correspondingly shaped half-shells lying one on the other. These each consist of cylindrical outer and inner shells with corresponding continuous elastomer/metal sheet/elastomer layers which are radially offset relative to one another so that they, or the full shell formed therefrom, are (is) eccentric in the un-tensioned state, but concentric or rotationally symmetrical after pre-tensioning.
These bushings, which were developed, in particular, for use in wind turbines in order to effect damping of arising vibrations, have, owing to their concentric geometry which is uniform in all directions, the disadvantage that they require a relatively large amount of space in all directions. However, the space available, especially in the horizontal plane, in gearbox bearing systems of wind turbines is very restricted. Since structure-borne sound in the wind turbines used arises principally through vertically directed vibrations, the damping systems must be designed to be correspondingly strong in this direction. For particularly good sonic properties, it is advantageous to have a relatively thick rubber layer in the direction of the solid-borne sound stimulation. In the rotationally symmetrical bushing of EP 1 046 832, the bushing would have to be larger in diameter, i.e. both in height and also in width, in order to improve the sonic properties. The supports or clamp halves would thus also have to be significantly widened, which results firstly in increased costs, greater weights, but also in stability problems in the upper half shell, meaning that the latter would have to be made significantly thicker owing to the greater bending moment given the greater clamping width. This in turn means that the space requirement in the horizontal direction is often not sufficient without corresponding modification measures having to be taken on the wind turbine.
The object was thus to develop a corresponding clamping bushing based on the clamping bushing of EP 1 046 832, which is effective per se, which on the one hand achieves improved damping or solid-borne sound decoupling in the vertical direction, but on the other hand requires a small or reduced space requirement in the horizontal direction.